Hemocyanin, tyrosinase and laccase are all copper-containing proteins which have a pair of contiguous Cu atoms important for biological activity. We propose to investigate mononuclear and binuclear Cu complexes as models for these proteins. Specifically we will 1) attempt to prepare stable dioxygen adducts derived from Copper(I) 2) examine mononuclear-binuclear analogues with the intent of contrasting O2 reactivity, 3) synthesize new binuclear copper complexes designed to have high, positive reduction potentials, 4) examine carbon monoxide reactions with binuclear copper(I) complexes with the intent of determining why hemocyanin and one model complex bind only a single CO, 5) attempt to establish the electronic and structural parameters conducive to five-coordination for Cu(I), 6) attempt to characterize autoxidation reaction intermediates and products.